The present invention relates to a method for forming a concrete block particularly, but not exclusively, a composite block having a base portion and a reflective fascia portion.
Throughout the specification and claims, use of the word xe2x80x9cblockxe2x80x9d is to be taken as including, for example, a curb stone, road divider or paver constructed wholly or in part of concrete or like substance.
A form of composite block is disclosed in GB2159556A. Such a block includes a base portion and a reflective fascia portion, and is formed by placing a base mix and facia mix in a mould and compressing same to remove excess water.
Another concrete block, in the form of a curb stone, is disclosed in GB2200936. The curb stone includes reflective material and is formed by randomly mixing the reflective material with fluid concrete, or pressing the material into the concrete when the curb stone is partially cured.
Both of the above known forms of concrete block are manufactured by a wet casting technique and curing of the blocks can take a considerable time, in the order of three days.
It is an object of the present invention to provide a method and apparatus for forming a block which utilises a dry casting technique. To the applicants knowledge, dry casting has never been used to manufacture curb stones for the reason that it is generally considered that dry casting would result in a block of inferior strength and durability and that the wet casting method was prescribed in order to meet the requirements for curb stones, as set out under British Standard BS 7263: Part 1: 1990, published by British Standards Institution, London. The present invention, however, utilises dry casting, in combination with a compacting step whereby the resultant block is capable of meeting the requirements of BS 6717: Part 1: 1993.
In accordance with the present invention there is provided a method of forming a concrete block comprising preparing a base mix, having a water/cement ratio of less than or substantially equal to 0.35, pouring the base mix into a mould and pressurising the mix by application of a compaction.
Preferably a fascia mix is poured into the mould prior to application of the compaction force whereby both the base mix and fascia mix are pressurised.
Preferably, the base mix is compressed prior to application of the compaction force so as to create a recess defined by the base mix and the mould, into which the fascia mix is poured.
Preferably the fascia mix includes reflective material. Alternatively, the facia mix is provided on a surface thereof with reflective material prior to compaction.
Preferably, a binding agent is provided between the base mix and facia mix prior to compaction.
Preferably the base mix is subjected to vibration prior to application of the compaction force so as to enhance filling of the mould and subsequent compaction.
Preferably preparing the base mix includes mixing cement with granite chips, not exceeding 9 mm in diameter, and sand particles not exceeding 5 mm in diameter, to enhance binding properties of the block.
In another aspect, there is provided an apparatus for effecting the above method including:
mixing means for mixing a base mix and a fascia mix;
a mould assembly including a mould and a feeder for receiving the base mix and fascia mix and transferring the base mix and fascia mix into the mould; and
a ram device for applying a compaction force to the mix held in the mould.
Preferably the mould assembly includes a vibration device for vibrating the mould to enhance filling of the mould and subsequent compaction.
Preferably the ram device is adapted for application of a vibro compaction force.
Preferably the feeder includes two portions for holding, respectively, the base mix and fascia mix, the feeder being arranged such that the portions are adapted to be alternately displaced over the mould for separate dispensing of the base mix and fascia mix within the mould.
In another aspect, there is provided a concrete block formed in accordance with the above described method.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.